Effect of annealing temperature on the thermoelectric properties of ZnInO thin films grown by physical vapor deposition

doi:10.1016/j.physb.2020.412569

Physica B: Condensed Matter

Volume 606, 1 April 2021, 412569

https://doi.org/10.1016/j.physb.2020.412569 Get rights and content

Abstract

This research work has been demonstrated the growth of ZnInO thin films using thermal evaporation technique for thermoelectric power generation applications. The pure zinc powder and indium metal were evaporated on the multi-crystalline Si substrate using the vacuum tube furnace. Deposited thin films were annealed at various temperatures (500–700 °C) for 30 min in a programmable muffle furnace. XRD data concluded that the sample annealed at temperature 500 °C^, has a weak structure of ZnO. But as we have increased the annealing temperature, indium atoms get thermal energy from the annealing process and reacted with ZnO molecule to form ZnInO composite. The vibrational and rotational modes of the samples were studied by the Raman spectroscopic analysis and morphology of annealed samples was verified by SEM. The Seebeck coefficient data suggested that the value of Seebeck coefficient varies between (140.9–182.2) μV/^oC. The maximum value of the Seebeck coefficient was obtained for the sample annealed at 600 °C because the mobility of carriers is highest at that temperature. But the value of electrical conductivity and power factor for the sample annealed at 600 °C is minimum due to low carrier concentration. Because of these conclusions, it may be suggested that this material can be a potential choice soon for thermoelectric power generation applications.

Introduction

Among transparent conducting oxides, Zinc Indium Oxide (ZIO) is supposed to be material of choice because of its high optical transparency, smooth surface, high conductivity and low deposition temperature. Due to these remarkable properties, it can be used in organic solar cells and sensors [1]. ZnInO thin films have been reported to be grown by several methods which include pulsed laser deposition, magnetron sputtering, sol-gel technique, metal-organic chemical vapor deposition method (MOCVD). The thermal evaporation technique has several advantages when compared with other methods due to its low deposition temperature and cost-effective technique [[2], [3], [4], [5]].

We talked about the environment pollution, the conventional energy sources such as gas, oil, and fossil fuels are causing a major portion of this pollution. Therefore, researchers are giving attention to the severe use of renewable energy sources which include fuel cells, photovoltaic cells, thermoelectric, nuclear power plants, wind and hydroelectric, etc. A significant reduction in the greenhouse gases emanating from the conventional energy sources can be made by thermoelectric devices [6]. Because it directly converts waste heat into useful energy, thermoelectric power generation is considered to be the potential source of renewable energy. It has some other benefits such as cost-effective maintenance and noise-free cheap electricity [7]. Thermoelectric materials are considered to be a key component for generating electric power from waste heat. For thermoelectric power generation applications, thermoelectric materials which have high stability and high figure of merit (ZT) are considered best [8]. The efficiency of any thermoelectric material can be improved by several ways reported in literature [9,10]. The dimensionless quantity that determines and evaluates the performance of a thermoelectric material is known as a figure of merit and is represented by the following formula $ZT = \frac{S^{2} σ T}{K}$ Where S is the Seebeck coefficient, σ is the electrical conductivity, K is the thermal conductivity and T is the absolute temperature [11,12]. According to this formula, the material which has a high Seebeck coefficient, high electrical conductivity and low thermal conductivity would consider to be a good thermoelectric material [13,14]. ZnInO supposed to be a good candidate to achieve a figure of merit more than unity due to its some properties such as stability at high temperature, modulation of electrical conductivity by the control of In atoms and easy nanostructure growth.

In the present research work, the thermoelectric potential of ZnInO nanostructures was investigated. The samples used in this study were deposited on multi-crystalline silicon substrate by the evaporation of Zn powder and indium metal in glass tube placed inside the tube furnace. The optimum value of the Seebeck coefficient, electrical conductivity and power factor was achieved by modulating the post-growth annealing temperature. XRD, SEM and Raman spectroscopy measurements were additionally performed to support our Seebeck results.

Section snippets

Experimental

The ZnInO nanostructures were grown on the multi-crystalline Silicon substrate by evaporating the zinc powder and indium metal mixed in 10:1 ratio placed in the glass tube. The 99.9% pure zinc powder and indium metal served as source material which was placed in the center of the glass tube. The multi-crystalline Silicon substrate was placed on the substrate holder and was kept at about 16 cm distance from the source material inside the glass tube. The whole assembly was placed in the tube

Results and discussion

The description of XRD patterns for samples annealed at different temperatures has been presented in Fig. 1. The sample annealed at 500 °C consisted of one diffraction peak at 47.4° which is related to the ZnO structure and was found in good agreement with the reported literature [[15], [16], [17], [18], [19]]. As we increased the annealing temperature, the intensity of this phase becomes low and it completely disappeared for the sample annealed at 700 °C. We have observed three new phases at

Conclusion

The manuscript reported the optimization of the Seebeck coefficient, electrical conductivity and power factor of ZnInO nanostructures using post-growth annealing method. Physical vapor deposited samples were subjected to high-temperature annealing in an oxygen environment in order to achieve enhanced thermoelectric properties. The highest value of the Seebeck coefficient was achieved for the sample annealed at 600 °C while electrical conductivity and power factor have higher values for the

Author agreement

It is verified that the submitted paper is original and has not been or is not being submitted to the peer review process to any other journal. It is further verified that all authors have checked the manuscript and are agree on submission to Optical Materials.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgement

This project was funded by the Deanship of Scientific Research (DSR), King Abdulaziz University, Jeddah, under grant No. (DF-691-135-1441). The authors, therefore, gratefully acknowledge DSR technical and financial support.

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Effect of annealing temperature on the thermoelectric properties of ZnInO thin films grown by physical vapor deposition

Abstract

Introduction

Section snippets

Experimental

Results and discussion

Conclusion

Author agreement

Declaration of competing interest

Acknowledgement

Appl. Surf. Sci.

Ceram. Int.

Phys. B Condens. Matter

Ceram. Int.

J. Alloys Compd.

Ceram. Int.

Opt. Mater.

Opt. Mater.

Opt. Mater.

Opt. Mater.

Optik

Mater. Char.

Transparent thin-film transistors with zinc indium oxide channel layer

J. Appl. Phys.